The present invention relates in general to respirators and, in particular, to a new and useful excess pressure respirator having an automatic or manual shutoff mechanism for stopping the flow of pressurized breathing gas when the respirator is not in use.
Circulating respirators with excess pressure in the respiratory cycle chamber ensure excess pressure during use both in the expiration and in the inspiration phase of the respiratory cycle. This excess pressure under any circumstances prevents penetration of ambient air into the respiratory cycle chamber which could be dangerous. Possible leaks in the apparatus only cause gas current from the inside to the outside.
All such known apparatus have the great disadvantage, however, that the breathing gas storage tanks must be closed at the end of use and removal of the oxygen mask, hence the opening of the respiratory cycle chamber, otherwise the breathing gas would flow off and the time which the apparatus can be used would be shortened.
This also applies to the known circulating respirator with excess pressure in the respiratory cycle described below. In such a device the breathing gas flows to the carrier and user of the device from a breathing bag through an inhaling tube with an inhaling valve just ahead of the oxygen mask. The exhaled gas arrives over an exhaling valve in the exhaling tube and through the tube and a CO.sub.2 absorber, back to the breathing bag. In order to build up the excess pressure, the breathing bag is loaded from the outside with a spring.
In order to protect the user, oxygen is supplied continuously to the breathing bag from the oxygen cylinder over a pressure reducer and additionally through an emergency valve. The emergency valve is controlled by movement of the breathing bag, which emergency may result from the movement of the breathing gas. The valve opens with the collapse of the breathing bag, and closes again with its inflation. Before removing the oxygen mask, the cylinder valve must be closed. If this not done, a large amount of oxygen will be lost because, when the respiratory cycle chamber is opened (this is done with the removal of the oxygen mask or in case of a large leak) the excess pressure drops. The breathing bag is thus compressed by the outer spring, and the emergency valve is opened. Oxygen thus can escape (see Brochure BP-0878, BioMarine Industries, Inc.).